NRC raises bar for San Onofre restart

Nuclear safety regulators are insisting that a damaged reactor at San Onofre must be safe to operate at full power before the operator can move forward with its restart plan.

San Onofre operator Southern California Edison wants to restart the plant's Unit 2 reactor at 70 percent power for a limited period as it looks for a long-term solution to the rapid degradation of recently replaced steam generators.

Nuclear Regulatory Commission officials, in a visit to U-T San Diego on Tuesday, said Edison has yet to address license specifications that the plant be able to run at full tilt.

"They either have to tell us that they think they're already compliant or they have to resubmit an operational analysis that demonstrates that they can operate the plant over a full range of power," said Arthur Howell, leader of the nuclear commission team evaluating the breakdown at San Onofre.

Edison spokeswoman Maureen Brown said the company is developing a response for nuclear regulators and it was "premature for us to comment on what is or is not required."

Howell and Gregory Warnick, chief resident inspector at San Onofre, spoke with U-T San Diego hours before a public meeting in Capistrano Beach about the agency's ongoing review of Edison's restart proposal. The commission's decision is due as soon as late-April or early-May.

It was unclear whether the license provision they cited might scuttle Edison's current plan or lead to a revision of the operating license.

"The spec says that they need to demonstrate tube integrity through all ranges of operation, which would be up to 100 percent, which his how the license is written," said Warnick, an inspector at the plant for the past five years. "They need to comply with the words of that specification."

The twin-reactor plant was shut down on Jan. 31, 2012, after a small radiation release was traced to a steam generator tube leak. Rapid wear was discovered among tubes that serve as a barrier to radiation and a crucial component of the reactors' cooling systems.

Edison wants to restart the Unit 2 reactor for five months to see if it can contain the rapid deterioration of tubing. The twin Unit 3 reactor has been set aside with more significant damage. The generators were replaced starting in 2009 at a cost of at least $670 million.

The most alarming wear on generator tubing has been traced to faulty computer modeling of steam flows in the design phase.

After plugging hundreds of tubes to isolate damaged tubes, Edison plans to prevent tubes from vibrating against each other by ratcheting down power at the plant. Monitoring equipment would be added, but regulators say little would be known about the advance of tube wear until the unit is taken offline against for further inspection.

Nuclear regulators are reviewing the reasonableness of that proposal in lengthy communications with Edison -- but say they must also adhere to provisions requiring safe operations at full power. Edison was notified of the issue in late December.